Aircraft: B767
Phase of flight: Parked
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Published Material / Policy; Ground Event / Encounter Ground Strike - Aircraft

The report is for an incident that occurred on company B767-300 aircraft. The aircraft received major damage to the front lower section of fuselage when the Nose Landing Gear (NLG) collapsed. The incident was initiated by a chronic leak of the Left Hydraulic System. I; Mechanic X; along with two other Mechanics; Y and Z; were trying to find the source of the hydraulic leak. According to the chronic paperwork attached to the Maintenance package of the aircraft that night; we had to service the Left Hydraulic System and perform visual checks of the rudders and tail section Aft Rigging Bay Compartment. Mechanic Y noticed hydraulic fluid leaking from the aft drain mast; so we proceeded to investigate the aft rigging bay. We then noticed hydraulic fluid all along the lower section of the aft tail rigging compartment; forward of the Tail Skid Actuator. We found the flexible hoses connected to the actuator saturated in hydraulic fluid; and also one the B-nut's on the Return line was loosen by half a turn. So we (Mechanic Y and I) proceeded to tighten the line and clean the [Tail Skid] actuator for leak checks. Now none of the mechanics; including myself; was familiar with the Tail Skid System on a B767s. So we all headed back to the Line Maintenance shack to research the Tail Skid System. We read through Chapter 32 and found the Tail Skid System in the Aircraft Maintenance Manual (AMM) 32-71-00). I found the Description and Operation (D/O) Manual and we (Mechanic Y and I) proceeded to read through the Manual for a better understanding of the system. After reading the manual; we (Mechanic Y and I) found a section (page 8 of 10) that talks about the retraction of the [Tail Skid] actuator. So we went back out to the aircraft after getting more supplies; and began to perform the retraction procedure for the actuator. I positioned myself in the Aft Tail section to observe any potential leak while Mechanic Y went to the cockpit and the other guy (Mechanic Z) positioned [himself] on the Scissor Lift Truck. I observed the actuator; looking for leaks as the strut began to retract. While performing the check; we kept in contact using our cellphones. The actuator moved to the fully retracted position and was seated flush against the fuselage; so we began the extension procedure and the aircraft shook violently. I was jarred from my position and fell on lower structure of the aircraft in the aft tail section. After gathering myself; I evacuated the tail section of the aircraft and proceeded to the front of the aircraft where I noticed the nose gear had collapsed causing structural damage. While troubleshooting a chronic hydraulic fluid leak; found Tail Skid Actuator leaking. Went inside [Line Maintenance shack] with Mechanic X and he pulled the Aircraft Maintenance Manual (AMM) reference up. After reading over; went outside to [aircraft] to tighten B-nut at actuator; then proceeded to [perform] Operational Check (Ops Ck) of [Tail Skid] System. Went upstairs [to cockpit]. While on telephone with Mechanic X and following AMM Manual; put hydraulics on; raised [Landing] Gear handle to 'Up' position; verified no leaks noted; returned handle to 'Down' position and turned hydraulics off; then the [Nose Landing] Gear collapsed. Later come to find out that the AMM Manual we were using was the Description/ Operation [section] and there was a more appropriate manual that could have been used to avoid this accident. Reporter stated the Description/ Operation (D/O) section of the Aircraft Maintenance Manual (AMM) for the Tail Skid operation did not have any reference directing mechanics to install Gear pins prior to operating the Gear handle. None of them had any General Familiarization (Gen Fam) classes on the B767 Aircraft Systems. They used their cell phones for communications between each other; instead of connecting hard wire headsets; because they did not know if there were any intercom jacks in the Tail Compartment. He was thrown around inside the Stabilizer compartment as the nose gear collapsed and struck the ground. Reporter stated that air bags were used to raise the nose section. The Nose gear was extended and the aircraft towed to a ramp location. His Air Carrier released a Maintenance Bulletin about the use of Gear pins and referencing proper manuals when performing maintenance. Another section was added to the Bulletin informing Mechanics to get help if they were unfamiliar with the work they were assigned. The Maintenance Bulletin also emphasized using the Adjustments and Tests procedures in the AMM when operating aircraft systems. Two Line Mechanics troubleshooting a chronic hydraulic leak and unfamiliar with B767-300 Aircraft Systems; cycle the Landing Gear handle with hydraulic pressure on using the Description/Operation (D/O) section of the Aircraft Maintenance Manual (AMM) instead of the Adjustments/Tests procedures. Gear pins were not installed; nose gear collapsed.